Unit 2 check
Unit 2 check: Cells
10 questions from 10 lessons in Unit 2. Answer each one, and if you miss, follow the link back to where it is taught, then try again. Your score counts first tries.
Question 1 · from 2.1 · Fill the statement
Complete the description of ribosomes.
A ribosome is built from and protein. Ribosomes are found in , which reflects the common ancestry of all known life, and each one joins amino acids in the order set by the sequence of its .
Question 2 · from 2.2 · Rank it
Four cells are modeled as simple shapes. Rank them by surface area-to-volume ratio.
Highest ratio first
Give each one a place, 1 for first. Give two the same place if they are equal.
Your ranking: none yet
Question 3 · from 2.3 · Match
Match each membrane component to its description.
Setup for question 4
A new experiment, a new question. A student hypothesizes that a drug which blocks channel proteins will lower the uptake of K⁺ into cells but not the uptake of O₂. She measures uptake into the same kind of cells with and without the drug, in units per minute. These numbers are a teaching example.
- K⁺ uptake: 50 without the drug, 4 with it
- O₂ uptake: 30 without the drug, 29 with it
Question 4 · from 2.4 · Calculate
By what percentage did the drug lower K⁺ uptake? Give your answer to the nearest whole percent.
Setup for question 5
A new substance, a new test. Cells are placed in a solution with substance T at 5 mM. After 30 minutes, cells given a poison that stops ATP production hold T at 5 mM inside, and untreated cells hold it at 40 mM inside. These numbers are a teaching example.
Question 5 · from 2.5 · Decide and justify
A student wants to check that the poison lowered uptake by stopping ATP production, not by damaging the cells in some other way. Which new investigation is better?
Which reason supports your decision?
Setup for question 6
A biologist measures how fast three substances cross three membranes, each time with the substance more concentrated on one side: an artificial bilayer with no proteins, a red blood cell membrane, and a red blood cell membrane treated with a drug that blocks aquaporins. Rates are in relative units. These numbers are a teaching example.
| Substance | Bilayer, no proteins | Red blood cell membrane | Red blood cell membrane, aquaporins blocked |
|---|---|---|---|
| Water | 1 | 50 | 3 |
| Glucose | 0.001 | 20 | 20 |
| O₂ | 100 | 100 | 100 |
Question 6 · from 2.6 · Calculate
Using the table: by what percentage did blocking aquaporins lower the rate at which water crosses the red blood cell membrane? Give your answer to the nearest whole percent.
Setup for question 7
A plant tissue's cells have a solute potential of −8 bars and a pressure potential of +2 bars, so their water potential is −6 bars. Samples of the tissue go into three open beakers at 27 °C (300 K), where pressure potential is 0. These numbers are a teaching example.
| Beaker | Solution | Ionization constant (i) |
|---|---|---|
| A | Pure water | none |
| B | 0.1 M sucrose | 1 |
| C | 0.4 M sucrose | 1 |
Question 7 · from 2.7 · Calculate
Using the table: what is the solute potential of the solution in beaker C, in bars? Give your answer to one decimal place.
Setup for question 8
A biologist measures Na⁺ and K⁺ inside nerve cells, and the difference in charge across their membranes (inside relative to outside, in millivolts), after 2 hours in each of three conditions. Outside the cells, Na⁺ is 145 mM and K⁺ is 5 mM throughout. These numbers are a teaching example.
| Condition | Na⁺ inside (mM) | K⁺ inside (mM) | Membrane potential (mV) |
|---|---|---|---|
| Normal | 12 | 140 | −70 |
| Na⁺/K⁺ pumps blocked | 60 | 90 | −40 |
| ATP production stopped | 58 | 92 | −42 |
Question 8 · from 2.8 · Multiple choice
Using the table: which explanation best fits the change in membrane potential when the pumps were blocked?
Question 9 · from 2.9 · Spot the error
A student explains why lysosomes are enclosed by a membrane. Tap the line with the mistake.
Question 10 · from 2.10 · Fill the statement
Complete the comparison of prokaryotic and eukaryotic cells.
Prokaryotes typically lack internal organelles but have internal regions with specialized functions, such as the , where their DNA is gathered. Eukaryotic cells maintain internal that partition the cell into specialized regions.
0 of 10 answered.